/* Hash Tables Implementation.
 *
 * This file implements in-memory hash tables with insert/del/replace/find/
 * get-random-element operations. Hash tables will auto-resize if needed
 * tables of power of two in size are used, collisions are handled by
 * chaining. See the source code for more information... :)
 *
 */

#include <stdint.h>

#ifndef __DICT_H
#define __DICT_H

#define DICT_OK 0
#define DICT_ERR 1

/* Unused arguments generate annoying warnings... */
#define DICT_NOTUSED(V) ((void) V)

// 真正数据的结构体
typedef struct dictEntry {
    void *key;          // 指针，指向一个 SDS，键值对的 key
    union {
        void *val;      // 指针，指向一个 RedisObject，键值对的 value
        uint64_t u64;   // 无符号 64 位整数
        int64_t s64;    // 有符号 64 位整数
        double d;       // double 浮点数   如果是数字且可以用8字节存下,就不需要再用指针指向 redisObject 了，因为指针也需要8字节
    } v;
    struct dictEntry *next; // next 指针，指向下一个 entry
} dictEntry;

typedef struct dictType {
    uint64_t (*hashFunction)(const void *key);

    void *(*keyDup)(void *privdata, const void *key);

    void *(*valDup)(void *privdata, const void *obj);

    int (*keyCompare)(void *privdata, const void *key1, const void *key2);

    void (*keyDestructor)(void *privdata, void *key);

    void (*valDestructor)(void *privdata, void *obj);
} dictType;

/* This is our hash table structure. Every dictionary has two of this as we
 * implement incremental rehashing, for the old to the new table. */
typedef struct dictht {
    dictEntry **table;          // 存放的数据，一个数组，每一个位置称为一个桶，可以存放一个或一组 dictEntry，通过 next 指针相连
    unsigned long size;         // 哈希桶 bucket 的数量，一定是2的指数幂
    unsigned long sizemask;     // size - 1，数据存放或查找时候要与 size 取模，取模的结果与 sizemask 相与一致，而且只需要计算一次
    unsigned long used;         // 已经存放的数据数量
} dictht;

typedef struct dict {
    dictType *type;     // 函数指针，寻找key时候的hash函数、比较函数、删除时候的析构函数
    void *privdata;     // 私有指针，由调用者在创建的时候传进来
    dictht ht[2];       // 真正存放数据的位置,ht[1]只在rehash的时候才有数据,其余时间为null
    long rehashidx;     // 此时 rehash 进行到的位置,-1 代表没有进行 rehash
    unsigned long iterators; /* number of iterators currently running */
} dict;

/* If safe is set to 1 this is a safe iterator, that means, you can call
 * dictAdd, dictFind, and other functions against the dictionary even while
 * iterating. Otherwise it is a non safe iterator, and only dictNext()
 * should be called while iterating. */
typedef struct dictIterator {
    dict *d;
    long index;
    int table, safe;
    dictEntry *entry, *nextEntry;
    /* unsafe iterator fingerprint for misuse detection. */
    long long fingerprint;
} dictIterator;

typedef void (dictScanFunction)(void *privdata, const dictEntry *de);

typedef void (dictScanBucketFunction)(void *privdata, dictEntry **bucketref);

/* This is the initial size of every hash table */
// dict 的初始桶大小
#define DICT_HT_INITIAL_SIZE     4

/* ------------------------------- Macros ------------------------------------*/
#define dictFreeVal(d, entry) \
    if ((d)->type->valDestructor) \
        (d)->type->valDestructor((d)->privdata, (entry)->v.val)

#define dictSetVal(d, entry, _val_) do { \
    if ((d)->type->valDup) \
        (entry)->v.val = (d)->type->valDup((d)->privdata, _val_); \
    else \
        (entry)->v.val = (_val_); \
} while(0)

#define dictSetSignedIntegerVal(entry, _val_) \
    do { (entry)->v.s64 = _val_; } while(0)

#define dictSetUnsignedIntegerVal(entry, _val_) \
    do { (entry)->v.u64 = _val_; } while(0)

#define dictSetDoubleVal(entry, _val_) \
    do { (entry)->v.d = _val_; } while(0)

#define dictFreeKey(d, entry) \
    if ((d)->type->keyDestructor) \
        (d)->type->keyDestructor((d)->privdata, (entry)->key)

#define dictSetKey(d, entry, _key_) do { \
    if ((d)->type->keyDup) \
        (entry)->key = (d)->type->keyDup((d)->privdata, _key_); \
    else \
        (entry)->key = (_key_); \
} while(0)

#define dictCompareKeys(d, key1, key2) \
    (((d)->type->keyCompare) ? \
        (d)->type->keyCompare((d)->privdata, key1, key2) : \
        (key1) == (key2))

#define dictHashKey(d, key) (d)->type->hashFunction(key)
#define dictGetKey(he) ((he)->key)
#define dictGetVal(he) ((he)->v.val)
#define dictGetSignedIntegerVal(he) ((he)->v.s64)
#define dictGetUnsignedIntegerVal(he) ((he)->v.u64)
#define dictGetDoubleVal(he) ((he)->v.d)
#define dictSlots(d) ((d)->ht[0].size+(d)->ht[1].size)
#define dictSize(d) ((d)->ht[0].used+(d)->ht[1].used)
#define dictIsRehashing(d) ((d)->rehashidx != -1)

/* API */
dict *dictCreate(dictType *type, void *privDataPtr);

int dictExpand(dict *d, unsigned long size);

int dictAdd(dict *d, void *key, void *val);

dictEntry *dictAddRaw(dict *d, void *key, dictEntry **existing);

dictEntry *dictAddOrFind(dict *d, void *key);

int dictReplace(dict *d, void *key, void *val);

int dictDelete(dict *d, const void *key);

dictEntry *dictUnlink(dict *ht, const void *key);

void dictFreeUnlinkedEntry(dict *d, dictEntry *he);

void dictRelease(dict *d);

dictEntry *dictFind(dict *d, const void *key);

void *dictFetchValue(dict *d, const void *key);

int dictResize(dict *d);

dictIterator *dictGetIterator(dict *d);

dictIterator *dictGetSafeIterator(dict *d);

dictEntry *dictNext(dictIterator *iter);

void dictReleaseIterator(dictIterator *iter);

dictEntry *dictGetRandomKey(dict *d);

unsigned int dictGetSomeKeys(dict *d, dictEntry **des, unsigned int count);

void dictGetStats(char *buf, size_t bufsize, dict *d);

uint64_t dictGenHashFunction(const void *key, int len);

uint64_t dictGenCaseHashFunction(const unsigned char *buf, int len);

void dictEmpty(dict *d, void(callback)(void *));

void dictEnableResize(void);

void dictDisableResize(void);

int dictRehash(dict *d, int n);

int dictRehashMilliseconds(dict *d, int ms);

void dictSetHashFunctionSeed(uint8_t *seed);

uint8_t *dictGetHashFunctionSeed(void);

unsigned long
dictScan(dict *d, unsigned long v, dictScanFunction *fn, dictScanBucketFunction *bucketfn, void *privdata);

uint64_t dictGetHash(dict *d, const void *key);

dictEntry **dictFindEntryRefByPtrAndHash(dict *d, const void *oldptr, uint64_t hash);

/* Hash table types */
extern dictType dictTypeHeapStringCopyKey;
extern dictType dictTypeHeapStrings;
extern dictType dictTypeHeapStringCopyKeyValue;

#endif /* __DICT_H */
